4 ms·

Mostly, I'm confused as to how this has only bitten people on Haswell - did pre-Haswell just enforce a MB invisibly there for some reason, or did Haswell explic

• wfunction 11y ago
  I'm wondering the same thing. The one thing I know that changed in Haswell is that the transactional memory instructions were found to be broken, but I assume those aren't the issue here...
• the8472 11y ago
  You have to remember that the absence of a barrier does not automatically causes concurrency failures in a fail-fast manner. The barriers just provide guarantees. Your code might end up working (either always or in 99.999999% of all observed operations) just by chance. So it might simply be more visible on haswell than on other systems because it behaves differently or is more aggressive about exploting non-barriered operations. From the mailing list: > In our case it's reproducing on 10 core haswells only which are different than 8 cores (dual vs single ring bus and more cache coherency options). It's probably a probability matter. [...] > Pinning the JVM to a single cpu reduces the probability of occurrence drastically (from a few times a day to weeks) so I'm guessing latency distributions may have an effect.